question about mtd_torturetest.c

[Gupta, Pekon]

> On Wed, 2013-01-23 at 15:25 +0800, Huang Shijie wrote:
> > Hi all:
> >
> >     The mtd_torturetest.c uses the 55/AA patterns to torture the nand
> block.
> > Are the 55/AA patterns more tougher then the random data?
> 
> Probably not, please, improve the test.
> 

(0x55/0xAA/0x55) pattern ensures that _all_ bits in the byte transition from 0-> 1, and 1->0,
Whereas, a random pattern may miss a bit-cell or miss transition sequence, of an bad bit-cell.
Exercising each bit both ways is important so as to differentiate a bad bit-cell (permanent error) from read-disturb errors (temporary error).

For read-disturb: http://download.micron.com/pdf/presentations/events/flash_mem_summit_jcooke_inconvenient_truths_nand.pdf


with regards, pekon